The present invention relates to improvements in clamping devices for tools particularly turning tools or lathes which include a support base having a plurality of guideways and at least one tool holder which is adjustable in the guideways and can be fixed in a predetermined position on the base by clamping means.
In accordance with a known prior art clamping arrangement, the guideways on the support base are in the form of a plurality of rods and the tool holder base has bores through which the rods extend to permit adjusting movement of the tool holder relative to the base. Cup springs placed on the rods and elastically pressing against the tool holder provide clamping means as well as a fine adjustment device for moving the tool holder against the cup springs. For stability purposes, the bores in the tool holder base through which the rods pass must be machined very accurately so that the tool holder can be moved directionally on the guides without much play and finally be secured in place in a desired predetermined position. Even with close tolerances, it has been found that excessive play developes between the rods and the complementary support bores of the tool holder over a period of time due to sliding wear. This play which develops over a period of use is particularly harmful in tool holders for turning bits or the like since it produces vibrations and undesirable chatter marks when turning a work piece to be machined.
With the foregoing in mind, it is an object of the present invention to provide an improved clamping arrangement for tools of the above mentioned type which is characterized by novel features of construction and arrangement facilitating adjustment of the tool holder on the support base in a very simplified manner wherein the holder can be locked firmly to the support base without play thereby eliminating vibrations and the deleterious chatter which produce the undesirable chatter marks on a finished workpiece. These features and advantages are provided in a device which is relatively easy and economical to manufacture. To this end, the base is provided with a plurality of guideways in the form of a series of elongated spaced side-by-side ribs which define a series of elongated grooves between the adjacent ribs. The tool support has a series of projections which engage in the grooves of the base and includes adjusting means operatively associated with the tool holder for effecting relative displacement of the projections in the grooves to effect firm pressure applying relation between the two when it is desired to fix the tool holder in a predetermined position on the base. Thus, the present invention provides an assembly wherein the tool holder can be adjusted over a wide range of positions on the base and locked in place by simple means providing an adjusting force between the grooves and projections so that the tool holder is mounted on the base without play and with a high rigidity.
More specifically, the support base is provided with a plurality of longitudinally oriented guideways arranged side by side in a common clamping plane arranged in two groups at opposite ends of the support base. The ribs at each end are preferably disposed angularly relative to one another and to the support base. Clamping means comprises at least one projection on the tool support which engages in a groove of the two groups of grooves in the base so that the projections of the groups are arranged mutually adjustable relative to one another by adjusting means against the wall of its respective groove in the base. The tool holder consists of a main section, an adjusting section, each having groups of projections complementing the groups of guideways in the base, the main section and the adjusting section being flexible in a cross direction and including means in the form of a screw member between the main section and the adjusting section actuatable in a predetermined manner to press the projections into pressure applying relation with the ribs on the base defining the grooves when it is desired to anchor or fix the tool in a predetermined position on the base.
By this construction, the tool holder may be adjusted step wise in a cross direction on the support base simply by slipping the holding projections into different grooves in the base of the respective groups of grooves. Additionally, the tool holder is infinitely adjustable in a longitudinal direction simply by moving its holding projections in the appropriate grooves of the support base. After longitudinal and cross direction adjustments of the tool holder, it may be locked in place by means of the adjusting means on the support base simply by actuating the adjusting screw member. In this fashion the holding projections of the main section of the tool holder which engage in one group of grooves in the support base are mutually adjusted and locked in relation to the holding projections of the adjusting section of the tool holder which engage in the other group of grooves.
In the preferred embodiment of the invention, the sidewalls of the projections defining the grooves of the two groups extend at an acute angle diagonally toward the opening of the grooves and the holding projections of the tool holder are disposed in a predetermined manner to be supported in the base of the grooves of the support base or on the outside surface of the support base located between the openings of the grooves
It has been found that by this arrangement a particularly reliable clamping action of the tool holder on the base is produced since the holding projections either are supported with their end surfaces in the base of the grooves of the support base or the outside surfaces located between the openings of the grooves. In this way during mutual adjustment of the holding projections, a force component results at the bevelled inside and outside walls defining the grooves between the tool holder and the support base oriented in a cross direction to the clamping plane. By reason of this force component, the holding projections are locked into the grooves or the outside surface of the base plate into the groove between the holding projections.
By constructing the tool holder of a main part and an adjusting part connected by a flexible connecting or bridging section, the tool holder is of comparatively simplified construction which can be made and assembled rather economically.
In accordance with one embodiment of the invention, the adjusting screw member is connected solidly with the main section of the tool holder fitted in the adjusting part oriented perpendicular to the grooves in the base. In accordance with another embodiment, the adjusting means are formed by a hydraulically activated movable adjusting plug mounted in the adjusting part of the tool holder perpendicular to the grooves and which is closely connected with the main section of the tool holder. This type of adjusting means is of rather simplified design and lends itself to automatic adjustment or an automatic tool holder exchange on the support base.
The cross section of at least one of the holding projections of the tool holder is preferably of a size and shape closely complementing the cross section of the mating grooves in the support base with little play in a transverse direction as well as in a direction perpendicular to the clamping plane so that the tool holder is held in place when assembling or slipping them in their holding projections and during subsequent longitudinal movement in the appropriate grooves when disassembling it from the support base.
In accordance with a feature of the invention, the holding projections are of rib-shaped configuration having flat side surfaces directly confronting the flat or planar sidewalls of the ribs defining the grooves in the base to provide large contact surfaces when locking the tool holder in place.